Semi-automatic firearms have been known for a long time. The first semi-automatic rifle was introduced in 1885. The M-16 automatic rifle has been used by the military for years. A civilian version of the M-16 is known as the AR-15 and is a semi-automatic rifle. The AR-15 has been manufactured and sold to civilians for many years. Standard AR-15 semi-automatic rifles are manufactured and distributed with an upper receiver and a lower receiver. The upper receiver and lower receiver are normally attached together at two locations by locking pins which pass through holes in the upper receiver and lower receiver. A locking pin in the front is known as the front takedown pin. A locking pin in the rear is known as the rear takedown pin. A user who wants to remove the upper receiver from the lower receiver to clean the internal action of the firearm must first remove the rear takedown pin and front takedown pin to allow access to the action of the firearm. Alternatively, if the user removes only the rear takedown pin, then the upper receiver can pivot away from the lower receiver with the front takedown pin acting as the pivot point.
Removing only the rear takedown pin allows a user to quickly separate the upper receiver from the lower receiver. However, this process has its flaws. A user can accidentally misplace the rear takedown pin. This would prevent the user from quickly reinserting the rear takedown pin and utilizing the firearm. What is needed is a firearm accessory which allows a user to remove the rear takedown pin to separate the upper receiver from the lower receiver without needed to completely removing the rear takedown pin from the complete firearm assembly.